Pulsepoint apps show you on a map the closest locations of Automatic Electronic Defibrillators (AED). They currently have over 91,000 registered and you can add more you know about. The apps are free and available for Android & iOS.
AEDs are fully automatic and have voice prompts to lead you through. They are completely "idiot proof," and the extreme stress of the moment can make idiots of any of us. They aren't cheap though; typically $1,300 and up. Consider getting one if you can afford it. I got one for my parents at a 30% off sale, though I don't know how often those happen.